EFFECT OF PARTICLE-SIZE AND TEMPERATURE ON EVOLUTION RATE OF VOLATILES FROM COAL

Pyrolysis runs were carried out in the temperature range ambient to 900 degrees C and the particle size range +38 to -2360 mu m on a low ash coal from the Waterberg area. Empirical correlations were established for the evolution rates of hydrogen, carbon monoxide and methane as a function of particle size and instantaneous temperature. The rate for hydrogen and carbon monoxide can be represented by an Arrhenius type equation incorporating particle size. The observations suggest that tar deposition is rate determining. The observations for the rate of evolution of methane suggest that it is governed by several complex reactions of which methanation and secondary cracking of tar are possibilities.